Creating an ArrayList of objects with a loop, checking for overlapping objects

Question

I'm making a game for a class and one element of the game is displaying a number of cabbages, which are stored in an ArrayList. This ArrayList must be a fixed number of 20, 10 of Good Cabbage and 10 of Bad Cabbage.

As the cabbages are created, I want to make sure they don't overlap when they are displayed. Where I'm running into trouble with this is that when I find a cabbage that overlaps, I'm not sure how to go back and create a new cabbage in its place. So far when the code finds an overlap, it just stops the loop. I guess I'm having trouble properly breaking out of a loop and restarting at the index that goes unfilled.

Here's what I have so far for this. Any suggestions would be much appreciated.

        // Initialize the elements of the ArrayList = cabbages
    // (they should not overlap and be in the garden) ....
    int minX = 170 ;
    int maxX = 480;
    int minY = 15;
    int maxY = 480;
    boolean r = false;
    Cabbage cabbage;
    for (int i = 0; i < N_GOOD_CABBAGES + N_BAD_CABBAGES; i++){
        if (i % 2 == 0){
        cabbage = new GoodCabbage((int)(Math.random()* (maxX-minX + 1))+ minX,
                (int)(Math.random()*(maxY-minY + 1))+ minY,window);
        } 
        else {
            cabbage = new BadCabbage((int)(Math.random()* (maxX-minX + 1))+ minX,
                    (int)(Math.random()*(maxY-minY + 1))+ minY,window);
            }
        if (i >= cabbages.size()){
        // compares the distance between two cabbages
            for (int j = 0; j < cabbages.size(); j++){
                Point c1 = cabbage.getLocation();
                Cabbage y = (Cabbage) cabbages.get(j);
                Point c2 = y.getLocation();
                int distance = (int) Math.sqrt((Math.pow((c1.x - c2.x), 2) + Math.pow((c1.y - c2.y),2)));
                if (distance <= (CABBAGE_RADIUS*2) && !(i == j)){
                    r = true;
                }
            }
        if (r){
            break;
            }
        cabbage.draw();
        cabbages.add(i, cabbage);
        }       
    }

Laurence Gonsalves · Accepted Answer · 2010-12-12 23:55:03Z

1

The easiest way to do this is probably to add another loop.

A do...while loop is suited to cases where you always need at least one iteration. Something like:

  boolean overlapped;
  do {
      // create your new cabbage here

      overlapped = /* check whether it overlaps another cabbage here */;
  } while (overlapped);

  cabbage.draw();
  cabbages.add(i, cabbage);

answered Dec 12, 2010 at 23:55

Laurence Gonsalves

144k38 gold badges264 silver badges315 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

kmitcham · Accepted Answer · 2010-12-13 00:30:13Z

0

It looks like you are making cabbage objects and then throwing them away, which is a (trivial) waste.

Why not pick the random X and Y, check if there is room at that spot, then make the cabbage when you have a good spot? You'll just churn through numbers, rather than making and discarding entire Objects. Plus you won't have to repeat the random location code for good and bad cabbages.

int x, y do { // pick x and y } while (cabbageOverlaps(x,y,list)

// create a cabbage at that x,y, and add it to list

boolean cabbageOverlaps(int x, int y, ArrayList existingCabbages)

answered Dec 13, 2010 at 0:30

kmitcham

162 bronze badges

Collectives™ on Stack Overflow

Creating an ArrayList of objects with a loop, checking for overlapping objects

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related